Light scanning devices of the above-mentioned type are used e.g. for a spatially resolved fluorescence examination of a sample. For this purpose, the above-mentioned device for generating the scanning light in the form of a single light beam produces a narrow beam, which is focussed onto the sample and which is rastered over the sample by means of a deflection device, e.g. in the form of tilting mirrors with two orthogonal tilting axes or axes of rotation in the optical path of the light beam, said light-generating device being a laser in most cases. The scanning light excites on the surface of a sample the generation of secondary light, e.g. in the form of fluorescent light. This secondary light is collected via an imaging optics and detected on a detection unit. Since the deflection unit irradiates, in a precisely definable manner, a respective specific spot on the sample in dependence upon the position of the tilting mirrors relative to one another and relative to the sample, a locally dependent statement with regard to the respective property of the sample can be made by means of the detection unit detecting the intensity of the secondary light.
The scanning time for measuring the whole sample depends on various parameters, such as the size of the angular field on the sample, the scanning increment, the spot size of the scanning beam on the sample, the integration time of the detection unit, the scanning or mirror velocity of the deflection unit as well as the desired signal-to-noise ratio. When samples with dimensions in the centimeter range are scanned with high spatial resolution by a scanning beam focussed to a few micrometers, the scanning times are in the range of minutes to hours. Such long scanning times are, however, a great problem for the operation of light scanning devices of this kind.